During cellular differentiation, daughter cells can have different fates. These fates may reflect the development of an organism, or they can be a manifestation of a pathology such as tumorigenesis. While significant progress has been made in understanding the regulatory mechanisms responsible for generating these different fates, how the asymmetry is initiated remains a central issue. I propose to investigate this question in a simple model system, the Gram-positive bacterium Bacillus subtilis that undergoes a form of asymmetric division. Several regulatory molecules involved in this process become localized to a site in the dividing bacteria separating the two cellular compartments destined to become the daughter cells. These patterns of localization suggest that asymmetry may derive from the particular orientation of the regulatory proteins at this site with respect to the two daughter cells. I propose a novel methodology to determine this orientation employing fusions of reporter proteins with a localized regulatory protein and assays of reporter activity using fluorescent microscopy. Knowledge of the spatial orientation of regulatory proteins may lead to-further understanding of how pathological cellular differentiation occurs.